Gathers information for time spent in the various managers or object (Film, Camera, etc.) being updated in Scene::device_update.
The stats include the total time spent in the device_update methods as well as time spent in subroutines (e.g. bvh build, displacement, etc.).
This does not qualify as a full blown profiler, but is useful to identify potential bottleneck areas.
The stats can be enabled and printed by passing `--cycles-print-stats` on the command line to Cycles, or `-- --cycles-print-stats` to Blender.
Reviewed By: brecht
Maniphest Tasks: T79174
Differential Revision: https://developer.blender.org/D8596
edd1164575